Drop ceilings for commercial and industrial buildings are well known. The drop ceiling is generally constructed of a metal framework of T-shaped members hung from the structural ceiling and forming a grid having a plurality of rectangular openings. The grid supports acoustical tiles or the like in the openings to form the drop ceiling surface. To provide overhead lighting in combination with drop ceiling construction, it has been the practice in the past to mount fluorescent lighting fixtures in the space above the drop ceiling frame and to provide a translucent panel flush with the drop ceiling below the fixture for diffusing light into the room.
In the past, the light diffusing panel has been supported in one of two ways to provide access to the light fixture for replacing bulbs from below. In one arrangement, the plastic light diffuser panel is supported directly on the drop ceiling framework. The light fixture, in the form of an open hood, is supported on the drop ceiling framework above the panel. This arrangement is relatively inexpensive, but removal of the light diffusing panel from below is cumbersome and time-consuming. This type of construction is not favored by the engineers and maintenance personnel. The alternative arrangement has been to construct the light diffuser panel and the light fixture as a unit with the light diffuser panel being mounted in a frame which is secured by hinges directly to the reflector hood of the light fixture. While this hinge arrangement simplifies the maintenance, the cost of the light fixture is substantially increased and more difficult and costly to install.